1. Field of the Invention
The present invention relates to a method and an apparatus for setting and adjusting a movement path of a coordinate measuring machine that measures the shape of a workpiece by scanning measurement.
2. Description of Related Art
A coordinate measuring machine that measures the shape of a workpiece by scanning measurement has been known.
FIG. 1 illustrates an exemplary configuration of a coordinate measuring system 10.
The coordinate measuring system 10 includes a coordinate measuring machine 20 and a computer terminal 40.
The coordinate measuring machine 20 includes a surface plate 21, a probe head 22, and a movement mechanism 30. A workpiece W is placed on the surface plate 21. The probe head 22 is used for scanning measurement of the workpiece W. The movement mechanism 30 allows the probe head 22 to three-dimensionally move in X, Y, and Z directions.
As illustrated in FIG. 1, an X, Y, and Z Cartesian coordinate system is set as a coordinate system of the machine for ease of illustration.
The X-direction corresponds to the horizontal direction in FIG. 1. The Y-direction corresponds to a direction into and out of the plane of FIG. 1. The Z-direction corresponds to the vertical direction in FIG. 1.
The movement mechanism 30 includes a gate-shaped frame 31, an X-slider 33, a Z-axis spindle 34, and a drive mechanism (not shown).
The gate-shaped frame 31 includes a cross beam 32 which is laid in the X-axis direction. The gate-shaped frame 31 is provided movably in the Y-axis direction.
The X-slider 33 includes a column having a length in the Z-axis direction. The X-slider 33 is provided slidably in the X-axis direction along the cross beam 32.
The Z-axis spindle 34 is inserted into the X-slider 33, and is provided slidably in the Z-axis direction.
The drive mechanism (not shown) includes a motor for driving the gate-shaped frame 31, the X-slider 33, and the Z-axis spindle 34 in the respective axis directions.
Assume herein that the shape of the workpiece W with turbine blades illustrated in FIG. 2 is measured by scanning measurement, for example.
The workpiece W has a structure in which a plurality of blades WB is mounted in parallel on a side surface of a main body WM. Assume herein that scanning measurement is performed to check if the shape of each blade WB is finished in conformity with designed values.
When a user sets a section S to be measured while viewing a screen 41 of the computer terminal 40, the computer 40 works out a scanning path SR based on the designed values of the workpiece W.
A contacting sphere 27 of the probe head 22 is moved along the scanning path SR to scan coordinates with a predetermined measurement pitch.
The term “scanning path SR” herein described refers to a path along the surface of the workpiece W to be measured.
The contacting sphere 27 is moved along the scanning path SR to thereby perform scanning measurement.
In order to move the contacting sphere 27 along the scanning path SR, it is necessary to appropriately move the probe head 22 according to the scanning path SR.
As illustrated in FIG. 3, a movement path MP of the probe head 22 is temporarily determined based on the scanning path SR and is displayed on the display screen 41, so that the user can confirm the movement path MP of the probe head 22 on the screen 41.
The “position of the probe head 22” corresponds to “a predetermined representative point within the probe head”. Examples of such a representative point include an uppermost point (a junction point with a lowermost end of the Z-axis spindle) of the probe head 22, a rotation center of the probe head 22, and an intersection of two rotation axes to be described later. Any point may be used as the representative point as long as it can represent the position of the probe head 22.
If the probe head 22 has a rotary joint or a swing joint, a joint point (a connection point between relatively movable members) of the rotary joint or the swing joint may be set as the representative point of the probe head 22.
The movement path MP which is automatically calculated by the computer terminal 40 according to the scanning path SR of the contacting sphere 27 is not appropriate in many cases.
For example, as illustrated in FIG. 4, assume that the movement path MP of the probe head 22 is generated so that the probe head 22 is positioned in the simplest manner in a direction perpendicular to the section S to be measured. In this case, a stylus 26 maintains a posture parallel with the Z-axis. As a result, the stylus 26 collides with the blades WB. Now, attention is turned to a region 900 which is surrounded by a dashed line in FIG. 4.
To avoid the collision mentioned above, when the stylus 26 is laid down to be in parallel with an XY plane, the stylus 26 and the probe head 22 may collide with a neighboring blade.
Accordingly, it is necessary for the user to make an adjustment so as to obtain an appropriate movement path for the probe head 22.